This invention relates to sealing containers, and more particularly to a machine and process for providing inserts having folded pull tabs.
In packaging foods in containers such as jars, bottles and tubs, it is important to form an impervious seal over the mouth of the container so that the contents of the container will not be contaminated during handling and storage. One very effective procedure for sealing such food containers, particularly containers having large mouths, utilizes foil that is heat sealed to the container rims. More particularly, the foil inserts are normally die cut from a large sheet of metal foil which has been coated with a heat sensitive adhesive. Each insert is installed in a lid that is formed from a polymer and is capable of fitting over and interlocking with the rim of a container. Thus, the lid places the insert directly over the container mouth. Thereafter the insert is heated sufficiently to render its adhesive coating pliable, and at the same time the lid is forced downwardly so that the foil insert is compressed tightly against the container rim. As the foil insert cools, the adhesive solidifies and thus bonds the insert to the rim. One highly effective procedure for heating the insert is to pass it through a rapidly oscillating magnetic field, and a machine for heating in this manner is disclosed in U.S. Pat. No. 4,095,390.
The lid into which the insert is installed prior to placement over the container mouth serves as a convenient carrier for the insert which by itself would be extremely difficult to handle, particularly during a heat sealing operation. Thus, the lid facilitates the actual placement of the insert over the container mouth and the inductive heat sealing of that insert to the container mouth. The lid further protects the somewhat fragile insert during handling and storage of the container, and once the insert is removed or ruptured to gain access to the contents of the container, the lid thereafter functions as a convenient closure for the container.
U.S. Pat. No. 4,230,028 discloses a machine for die cutting foil inserts from sheet foil and for installing those inserts in container lids on a rapid and highly automated basis. However, the machine cuts inserts that correspond in configuration to that of the lid and container rim. It does not have the capability of installing inserts provided with pull tabs. In this regard, some food packager prefer to have pull tabs on the inserts of their containers, so that once the lid is removed, the inserts can be peeled off of the container rim by grasping it at its pull tab and pulling upwardly.